Film forming method and film forming apparatus

ABSTRACT

The invention includes inserting an object to be processed into a processing vessel, which can be maintained vacuum, and making the processing vessel vacuum; performing a sequence of forming a ZrO 2  film on a substrate by alternately supplying zirconium source and an oxidizer into the processing vessel for a plurality of times and a sequence of forming SiO 2  film on the substrate by alternately supplying silicon source and an oxidizer into the processing vessel for one or more times, wherein the number of times of performing each of the sequences is adjusted such that Si concentration of the films is from about 1 atm % to about 4 atm %; and forming a zirconia-based film having a predetermined thickness by performing the film forming sequences for one or more cycles, wherein one cycle indicates that each of the ZrO 2  film forming sequences and the SiO 2  film forming sequences are repeated for the adjusted number of times of performances.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application claims the benefit of Japanese Patent Application No.2008-206976, filed on Aug. 11, 2008, in the Japan Patent Office, thedisclosure of which is incorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and an apparatus for forming azirconia-based film on a substrate to be processed, such as asemiconductor wafer.

2. Description of the Related Art

Recently, due to demands for higher integration and higher operatingspeed of a large scale integration (LSI), design rules of semiconductordevices that constitute a LSI are becoming finer. Along with thedemands, there are also demands for increased capacity of capacitorsthat are used in dynamic random access memories (DRAMs) and demands forincreased permittivity of dielectric films. It is necessary tocrystallize such dielectric films to obtain higher permittivity, andthus a film with higher crystallinity is demanded. Furthermore, sincesome devices have limits in thermal budget, a film which may be formedor crystallized at a low temperature is demanded.

A zirconium oxide (ZrO₂) film is considered as a film with highpermittivity, which is applicable to the above purposes, (see Reference1).

Known techniques for forming a zirconium oxide film at a low temperatureinclude an atomic layer deposition (ALD) process, in which source gas(precursor), e.g. tetrakis(ethylmethylamino)zirconium (TEMAZ), andoxidizer, e.g. O₃ gas, are supplied alternately (see Reference 2).Furthermore, zirconium oxide may be easily crystallized, and may becrystallized without inflicting negative effects on a device by forminga film at a low temperature by using the technique as described aboveor, additionally, annealing the film at a low temperature less than orequal to 450° C.

Such a dielectric film is required to exhibit not only high permittivitybut also low leakage current. However, when a dielectric film iscrystallized as described above, leakage current increases due toleakage from grain boundaries of crystals.

[Reference 1] Japanese Laid-Open Patent Publication No. 2001-152339

[Reference 2] Japanese Laid-Open Patent Publication No. 2006-310754

BRIEF SUMMARY OF THE INVENTION

To solve the above and/or other problems, the present invention providesa film forming method and a film forming apparatus for forming azirconia-based film that is crystallized and exhibits small leakagecurrent.

The present invention also provides a computer readable recording mediumhaving recorded thereon the film forming method of forming azirconia-based film.

According to an aspect of the present invention, there is provided afilm forming method including inserting objects to be processed into aprocessing vessel that can be maintained vacuum, and making theprocessing vessel vacuum; performing a sequence of forming a ZrO₂ filmon a substrate by alternately supplying a zirconium source and anoxidizer to the processing vessel a plurality of times and performing asequence of forming a SiO₂ film on the substrate by alternatelysupplying a silicon source and the oxidizer to the processing vessel oneor more times, wherein the number of times of performances of each ofthe sequences is adjusted such that Si concentration of the films isfrom about 1 atm % to about 4 atm %; and forming a zirconia-based filmhaving a predetermined thickness by performing the film formingsequences for one or more cycles, wherein one cycle indicates that eachof the ZrO₂ film forming sequences and the SiO₂ film forming sequencesare repeated the adjusted number of times of performances.

Here, the number of times the zirconium source and the oxidizer aresupplied during the formation of the ZrO₂ film and the number of timesthe silicon source and the oxidizer are supplied during the formation ofthe SiO₂ film may be adjusted such that the Si concentration of each ofthe films is from about 2 atm % to about 4 atm %.

Furthermore, a gas remaining in the processing vessel may be exhaustedbetween the supplying of the zirconium source and the supplying of theoxidizer and between the supplying of the silicon source and thesupplying of the oxidizer. After forming the zirconia-based film, theobtained films may be annealed at a temperature lower than or equal to450° C.

Furthermore, the oxidizer may be at least one selected from the groupconsisting of O₃ gas, H₂O gas, O₂ gas, NO₂ gas, NO gas, N₂O gas, and aradical of O₂ gas and H₂ gas. The zirconium source and the siliconsource may be organic metal compounds. It is preferable that the formedzirconia-based film has zirconia crystals. Also, it is preferable thatthe Si concentration of the films is adjusted in proportion to a ratioof the number of times which the Si source is supplied.

According to another aspect of the present invention, there is provideda film forming apparatus for forming a metal oxide layer with respect toobjects to be processed, the film forming apparatus including avertically cylindrical processing vessel which can be maintained vacuum;a supporting unit which supports the objects to be processed within theprocessing vessel; a heating unit which is formed to surround the outersurface of the processing vessel; a zirconium source supplying unitwhich supplies a zirconium source to the processing vessel; a siliconsource supplying unit which supplies a silicon source to the processingvessel; an oxidizer supplying unit which supplies an oxidizer to theprocessing vessel; and a control unit which controls the zirconiumsource supplying unit, the silicon source supplying unit, and theoxidizer supplying unit, wherein the control unit controls the filmforming apparatus: to insert the objects to be processed into aprocessing vessel, which can be maintained vacuum, to make theprocessing vessel vacuum; to perform a sequence of forming a ZrO₂ filmon a substrate by alternately supplying the zirconium source and anoxidizer to the processing vessel a plurality of times and to perform asequence of forming a SiO₂ film on the substrate by alternatelysupplying the silicon source and the oxidizer to the processing vesselone or more times, wherein the number of times of performances of eachof the sequences is adjusted such that Si concentration of the films isfrom about 1 atm % to about 4 atm %; and to perform the film formingsequences for one or more cycles, wherein one cycle indicates that eachof the ZrO₂ film forming sequences and the SiO₂ film forming sequencesare repeated the adjusted number of times of performances.

Here, the control unit may control the film forming apparatus such thatthe number of times the zirconium source and the oxidizer are suppliedduring the formation of the ZrO₂ film and the number of times thesilicon source and the oxidizer are supplied during the formation of theSiO₂ film are adjusted, so that the Si concentration of each of thefilms is from about 2 atm % to about 4 atm %.

Furthermore, the control unit may control the film forming apparatussuch that a gas remaining in the processing vessel is exhausted betweenthe supplying of the zirconium source and the supplying of the oxidizerand between the supplying of the silicon source and the supplying of theoxidizer. Furthermore, after forming zirconia-based film comprising theZrO₂ film and the SiO₂ film, the control unit may control the filmforming apparatus such that the obtained films are annealed at atemperature lower than or equal to 450° C. Also, it is preferable thatthe Si concentration of the films is adjusted in proportion to a ratioof the number of times which the Si source is supplied.

According to another aspect of the present invention, there is provideda computer readable recording medium having recorded thereon a computerprogram for executing the film forming method of any one of claims 1through 8.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detail exemplary embodimentsthereof with reference to the attached drawings in which:

FIG. 1 is a longitudinal sectional view of a film forming apparatus forexecuting a film forming method according to an embodiment of thepresent invention;

FIG. 2 is a cross-sectional view of the film forming apparatus of FIG.1;

FIG. 3 is a timing chart showing timings of gas supply performed in afilm forming method according to an embodiment of the present invention;

FIG. 4 is a graph showing a relationship between a ratio of the numberof times a SiO₂ film forming sequence is performed and Si concentrationof a film;

FIG. 5 is a graph showing relationships among Si concentration of afilm, permittivity of the film, and leak current of the film;

FIG. 6 is a transmission electron microscopic (TEM) photograph of asample 6 (Si=0 atm %), a sample 1 (Si=3.1 atm %), and a sample 2 (Si=5.5atm %);

FIG. 7 is a diagram showing crystal structures of the sample 6 (Si=0 atm%) and the sample 1 (Si=3.1 atm %) confirmed using electron beamdiffraction; and

FIG. 8 is a graph showing relationships between a ratio of the number oftimes a SiO₂ film forming sequence is performed and Si concentration ofa film, in cases where 3DMAS and 4DMAS are respectively used as Sisource.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention will be described in detail byexplaining exemplary embodiments of the invention with reference to theattached drawings.

FIG. 1 is a longitudinal sectional view of a film forming apparatus forexecuting a film forming method according to an embodiment of thepresent invention, FIG. 2 is a cross-sectional view of the film formingapparatus of FIG. 1, and FIG. 3 is a timing chart showing timings of gassupply performed in a film forming method according to an embodiment ofthe present invention. Furthermore, a heating unit is omitted in FIG. 2.

The film forming apparatus 100 includes a cylindrical processing vessel1 of which bottom is open and which has a ceiling. The processing vessel1 is entirely formed of quartz, for example, and a top plate 2 formed ofquartz is formed at the ceiling of the processing vessel 1 and seals theceiling of the processing vessel 1. Furthermore, a manifold 3, which maybe formed of stainless steel and may have a cylindrical shape, isconnected to the open bottom of the processing vessel 1 via a sealingmember 4, such as an O-ring.

The manifold 3 supports the bottom of the processing vessel 1, and awafer boat 5 formed of quartz, on which a plurality of semiconductorwafers (hereinafter referred as wafers W), e.g. from 50 to 100 wafers W,as objects to be processed may be stacked in multiple layers, may beinserted from below the manifold 3 into the processing vessel 1. Thewafer boat 5 includes three pillars 6 (refer to FIG. 2), and a pluralityof wafers W are supported by grooves formed in the pillars 6.

The wafer boat 5 is disposed on a table 8 via a thermos vessel 7 formedof quartz, and the table 8 is disposed on and supported by an rotatingshaft 10 which penetrates a cover unit 9 for opening and closing theopen bottom of the manifold 3, wherein the cover unit 9 may be formed ofstainless steel.

A magnetic fluid seal 11 may be formed where the rotating shaft 10penetrates the cover unit 9, and closely seals the rotating shaft 10 androtatably supports the rotating shaft 10. Furthermore, a sealing member12, which may be an O-ring, is interposed between the peripheral portionof the cover unit 9 and the bottom surface of the manifold 3, tomaintain sealing of the processing vessel 1.

The rotating shaft 10 is attached to a leading end of an arm 13supported by an elevating mechanism (not shown), such as a boatelevator, and is configured to elevate the wafer boat 5 and the coverunit 9 together so as to be inserted into and pulled out from theprocessing vessel 1. Also, the table 8 may be formed fixed to the coverunit 9, and the wafers W may be processed without rotating the waferboat 5.

The film forming apparatus 100 includes an oxidizer supply mechanism 14,which supplies an oxidizer gas (e.g. O₃ gas) into the processing vessel1, a Zr source gas supply mechanism 15, which supplies Zr source gas(zirconium source material) into the processing vessel 1, and a Sisource gas supply mechanism 16, which supplies Si source gas (siliconsource material) into the processing vessel 1. Furthermore, the filmforming apparatus 100 further includes a purge gas supply mechanism 28,which supplies an inert gas (e.g. N₂ gas) as a purge gas into theprocessing vessel 1.

The oxidizer supply mechanism 14 includes: an oxidizer source 17; anoxidizer piping 18 which guides an oxidizer from the oxidizer source 17;and an oxidizer spreading nozzle 19, wherein the oxidizer spreadingnozzle 19 is a pipe which is formed of quartz, is connected to theoxidizer piping 18, penetrates a sidewall of the manifold 3 inwardly, isbent upward, and vertically extends upward. A plurality of gas ejectingholes 19 a are formed apart from each other in the vertically extendingportion of the oxidizer spreading nozzle 19, so that the oxidizer, e.g.O₃ gas, may be ejected from each of the gas ejecting holes 19 a almostuniformly in a horizontal direction toward the processing vessel 1.Examples of the oxidizer may be not only O₃ gas, but also be H₂O gas, O₂gas, NO₂ gas, NO gas, N₂O gas, or the like. A plasma generatingmechanism may be formed to plasmarize an oxidizer so as to obtain higherreactivity. Also, O₂ gas and H₂ gas may be used for radical oxidization.In case of using O₃ gas, it is assumed that an ozonizer, which generatesO₃ gas, is disposed as the oxidizer source 17.

The Zr gas supply mechanism 15 includes a Zr source container vessel 20,which contains liquefied Zr source (e.g.tetrakis(ethylmethylamino)zirconium; TEMAZ), a Zr source piping 21,which guides the liquefied Zr source from the Zr source container vessel20, a vaporizing unit 22, which is connected to the Zr source piping 21and evaporates the liquefied Zr source, a Zr source gas piping 23, whichguides Zr source gas generated by the vaporizing unit 22, and a Zrsource gas spreading nozzle 24, wherein the Zr source gas spreadingnozzle 24 is a pipe which is formed of quartz, is connected to the Zrsource gas piping 23, penetrates a sidewall of the manifold 3 inwardly,is bent upward, and vertically extends upward. A carrier gas piping 22a, which supplies N₂ gas as carrier gas, is connected to the vaporizingunit 22. A plurality of gas ejecting holes 24 a are formed apart fromeach other in the vertically extending portion of the Zr source gasspreading nozzle 24, so that Zr source gas may be ejected from each ofthe gas ejecting holes 24 a uniformly in a horizontal direction into theprocessing vessel 1.

The Si source gas supply mechanism 16 includes a Si source containervessel 25, which contains liquefied Si source (e.g.trisdimethylaminosilane; 3DMAS), a heater 25 a, which is formed aroundthe Si source container vessel 25 to evaporate liquefied Si source, a Sisource gas piping 26, which guides Si source gas evaporated by thevaporizing unit 22 in the Si source container vessel 20, and a Si sourcegas spreading nozzle 27, which is connected to the Si source gas piping26 and penetrates a sidewall of the manifold 3. A plurality of gasejecting holes 27 a are formed apart from each other on the Si sourcegas spreading nozzle 27 in the lengthwise direction of the Si source gasspreading nozzle 27, so that Si source gas may be ejected from each ofthe gas ejecting holes 27 a almost uniformly in horizontal directioninto the processing vessel 1.

Furthermore, the purge gas supply mechanism 28 includes a purge gassupply source 29, a purge gas piping 30, which guides purge gas from thepurge gas supply source 29, and a purge gas nozzle 31, which isconnected to the purge gas piping 30 and penetrates a sidewall of themanifold 3. An inert gas, e.g. N₂ gas, may be suitable as the purge gas.

An opening valve 18 a and a flux controller 18 b, such as a mass-flowcontroller, are formed on the oxidizer piping 18, so that flux ofoxidizer gas to be supplied may be controlled. Furthermore, an openingvalve 26 a and a flux controller 26 b, such as a mass-flow controller,are also formed on the Si source gas piping 26, so that flux of Sisource gas to be supplied may be controlled. Furthermore, an openingvalve 30 a and a flux controller 30 b, such as a mass-flow controller,are formed on the purge gas piping 30, so that flux of purge gas to besupplied may be controlled.

A Zr source pumping pipe 20 a is inserted into the Zr source containervessel 20, and liquefied Zr source is supplied to the Zr source piping21 by supplying a pumping gas, e.g. He gas, via the Zr source pumpingpipe 20 a. A flux controller 21 a, such as a liquid mass-flowcontroller, is formed on the Zr source pressurizing pipe 21, whereas avalve 23 a is formed on the Zr source gas pipe 23.

There are no limits in Zr source, and various types of Zr sources may beused as long as a ZrO₂ film may be formed. From among Zr sources, anorganic metal compound that is liquid at the room temperature, such asTEMAZ stated above, may be suitable. Also,tetrakis(diethylamino)zirconium, which is another organic metal compoundthat is liquid at the room temperature, may be used. A Zr source that issolid at the room temperature may also be used. However, in this case, amechanism for evaporizing the Zr source and a mechanism for heating apipe are further required.

There are no limits in Si source, and various types of Si sources may beused as long as a SiO₂ film may be formed. From among Si sources, anorganic metal compound, such as 3DMAS stated above, may be suitable.Also, other organic metal compounds, such as tetra-dimethylaminosilane(4DMAS) and bis(tertiärbutylamino)silane (BTBAS), may be used as Sisource.

The oxidizer spreading nozzle 19 for ejecting and spreading an oxidizeris formed in a concave portion 1 a of the processing vessel 1, and theZr source gas spreading nozzle 24 and the Si source gas spreading nozzle27 are formed to interpose the oxidizer spreading nozzle 19therebetween.

An exhaust hole 37 for vacuum-exhausting the processing vessel 1 isformed on a portion of the sidewall of the processing vessel 1, theportion being opposite to a portion in which the oxidizer spreadingnozzle 19 and the Zr source gas spreading nozzle 24 are formed. Theexhaust nozzle 37 is formed to be long and narrow by cutting a portionof the sidewall of the processing vessel 1 in vertical direction. Aexhaust hole covering unit 38, which has a U-shaped cross-section tocover the exhaust hole 37, is weld-attached to the portion of theprocessing vessel 1, the portion corresponding to the exhaust hole 37.The exhaust hole covering unit 38 extends upward along the sidewall ofthe processing vessel 1, and defines a gas outlet 39 that extends upwardalong the processing vessel 1. Furthermore, gas in the processing vessel1 is vacuum-sucked from the gas outlet 39 by a vacuum-exhaustingmechanism (not shown), such as a vacuum pump. Furthermore, a heatingunit 40 that has a barrel shape and heats the processing vessel 1 andthe wafers W therein is formed to surround the outer surface of theprocessing vessel 1.

A controller 50, which includes a microprocessor (computer), controlseach of components of the film forming apparatus 100. For example, thecontroller 50 controls supplying/stopping of each of gas byopening/closing the valves 18 a, 23 a, 26 a, and 30 a, controls flux ofgas or liquefied source via the flux controllers 18 b, 21 a, 26 b, and30 b, switches gas injected into the processing vessel 1, and controlsthe heating unit 40. A user interface 51 is connected to the controller50 so that an operator may manage the film forming apparatus 100. Theuser interface 51 may be a keyboard to input commands, a displayapparatus to visually display operational status, or the like.

Furthermore, a memory device 52, which contains a recipe, such as, acontrol program, which instructs to perform various operations of thefilm forming apparatus 100 under the control of the controller 50, or aprogram for instructing each of the components of the film formingapparatus 100 to execute a particular operation, is connected to thecontroller 50. The recipe is stored in a recording medium in the memorydevice 52. The recording medium may be a fixedly formed one such as ahard disk, or may be a mobile one such as a CD-ROM, a DVD, and a flashmemory. Also, recipes may be transmitted from another apparatus via adedicated line.

Furthermore, if required, a desired operation may be performed by thefilm forming apparatus 100 under the control of the controller 50 byloading a random recipe from the memory unit 52 according to aninstruction from the user interface 51 and performing the random recipe.

Next, a film forming method performed in the film forming apparatus 100having a configuration as described above will be described in referenceto FIG. 3.

First, at the room temperature, the wafer boat 5, on which a pluralityof wafers W, e.g. from 50 to 100 wafers W, are stacked, is loaded intothe processing vessel 1, which is set at a predetermined temperature inadvance, by being lifted from below the processing vessel 1, and theopening on the bottom surface of the manifold 3 is covered with thecover unit 9 so that the processing vessel 1 is tightly sealed. Forexample, the diameter of the wafer W is 300 mm.

Then, the processing vessel 1 is vacuum-sucked to maintain the internalpressure of the processing vessel 1 at a predetermined processingpressure. At the same time, power supplied to the heating unit 40 iscontrolled to increase the temperature of the wafers W to a processingtemperature, and the wafer boat 5 is rotated. In this state, a filmforming process begins. The processing temperature may be from about200° C. to about 300° C., and may be 210° C., for example.

During the film forming process, as shown in FIG. 3, one ZrO₂ filmforming sequence includes an operation S1 of supplying Zr source gasinto the processing vessel 1 so that the Zr source gas is adhered to thewafers W, an operation S2 of purging the interior of the processingvessel 1 by using purge gas, an operation S3 of oxidizing the Zr sourcegas by supplying a gas-state oxidizer (e.g. O₃ gas) into the processingvessel 1, and an operation S4 of purging the interior of the processingvessel 1 by using purge gas, and a ZrO₂ film is formed by repeating theZrO₂ film forming sequence for x times (x is an integer equal to orgreater than 2).

Next, one SiO₂ film forming sequence includes an operation S5 ofsupplying Si source gas into the processing vessel 1 so that the Sisource gas is adhered to the wafers W, an operation S6 of purging theinterior of the processing vessel 1 by using purge gas, an operation S7of oxidizing the Si source gas by supplying a gas-state oxidizer (e.g.O₃ gas) into the processing vessel 1, and an operation S8 of purging theinterior of the processing vessel 1 by using purge gas, and a SiO₂ filmis formed by repeating the SiO₂ film forming sequence for y times (y isan integer equal to or greater than 1).

x times of ZrO₂ film forming sequences and y times of SiO₂ film formingsequences are considered as one cycle, and the cycle is repeated for ztimes, so that a film has a predetermined thickness. The z is set tohave a suitable value, that is, 1 or greater, according to a desiredthickness of a zirconia-based film. Furthermore, the order of theformation of the ZrO₂ film and the formation the SiO₂ film may bereverse.

Next, a crystallized zirconia-based film is formed by annealing the filmif required. In this case, an annealing temperature may be lower than orequal to 450° C. If the annealing temperature exceeds 450° C., it maycause adverse effects to a semiconductor device.

Here, the values of x and y are determined such that Si concentration ofthe zirconia-based film is from about 1 atm % to about 4 atm %. If Siconcentration is less than 1 atm %, no sufficient effects are obtained.On the other hand, if Si concentration exceeds 4 atm %, a film which isformed becomes amorphous, and thus permittivity of the film is lowered.Preferably, Si concentration of a zirconia-based film is from about 2atm % to about 4 atm %.

Si concentration in a zirconia-based film is almost proportional toy/(x+y), which is a ratio of the number of times y which Si source issupplied. For example, in case where TEMAZ is used as Zr source, 3DMASis used as Si source, a film is formed according to the film formingmethod described above under conditions of 1 Torr (133.3 Pa) and 210°C., and the film is then annealed at 450° C., a relationship betweeny/(x+y)×100[%] and Si concentration [atm %] in the film is as shown inFIG. 4. Detailed descriptions regarding FIG. 4 will be given below. Forexample, as shown in FIG. 4, to obtain a film of which Si concentrationis 3 atm %, it is clear that a ratio of y, (y/(x+y)×100)(%), may beabout 8.3%, that is, the number of times y the SiO₂ film formingsequence is performed may be 1 when the number of times x the ZrO₂ filmforming sequence is performed is 11. If the graph as shown in FIG. 4 isprepared in advance, a film may be formed with suitable x value and yvalue to obtain desired Si concentration.

In the operation S1, Zr source, e.g. TEMAZ, is supplied from the Zrsource container vessel 20 of the Zr source gas supplying unit 15, andZr source gas, which is generated by vaporizing the Zr source using thevaporizing unit 22, is supplied into the processing vessel via the Zrsource gas piping 23 and the Zr source gas spreading nozzle 24 for atime period T1. Thus, Zr source is adhered to the wafers W. Here, forexample, the time period T1 may be from 1 second to 120 seconds.Furthermore, for example, the flux of Zr source may be from about 0.2mL/min(sccm) to about 0.5 mL/min(sccm). Furthermore, for example, theinternal pressure of the processing vessel 1 may be from about 10 Pa toabout 100 Pa.

In the operation S3 of supplying an oxidizer, an oxidizer, e.g. O₃ gas,is ejected from the oxidizer source 17 of the oxidizer supplying unit 14via the oxidizer piping 18 and the oxidizer spreading nozzle 19.Therefore, the Zr source attached to the wafers W is oxidized, and thusZrO₂ is obtained.

Preferably, a time period T3 for performing the operation S3 may be from10 seconds to 180 seconds. Although the flux of the oxidizer variesaccording to the number of wafers W stacked or the type of oxidizer, theflux of the oxidizer may be, for example, from about 100 g/Nm³ to about200 g/Nm³, in case where O₃ gas is used as the oxidizer and from 50 to100 wafers W are stacked. Furthermore, for example, in this case, theinternal pressure of the processing vessel 1 may be from about 10 Pa toabout 100 Pa.

The operations S2 and S4 are operations of purging a gas remaining inthe processing vessel 1 after the operation S1 or the operation S3, sothat a desired reaction may occur during next operation. In theoperations S2 and S4, the purge gas supply source 29 of the purge gassupplying unit 28 supplies purge gas, e.g. N₂ gas, into the processingvessel 1 via the purge gas piping 30 and the purge gas nozzle 31, sothat the interior of the processing vessel 1 is purged. In this case,vacuum-sucking and supplying purge gas may be repeated for a pluralityof times to increase efficiency of removing remaining gas. Time periodsT2 and T4 respectively for the operations S2 and S4 may be from 20seconds to 120 seconds. Furthermore, for example, the internal pressureof the processing vessel 1 may be from about 10 Pa to about 100 Pa. Atthis point, the operation S2 after the operation S1 of supplying Zrsource gas and the operation S4 after the operation S3 of supplying anoxidizer may employ respectively different time periods forvacuum-sucking and supplying purge gas, in consideration of a differencebetween the degrees of exhaustions of gases in the operations S2 and S4.More particularly, time periods regarding the operation S2 may be longerthan those regarding the operation S4, because it takes longer timeperiod to exhaust gas after the operation S1 than the operation S3.

In the operation S5, Si source, e.g. 3DMAS, contained in the Si sourcecontainer vessel 25 of the Si source gas supplying unit 16, is vaporizedby the heater 25 a, and Si source gas generated by the vaporization issupplied into the processing vessel 1 via the Si source gas piping 26and the Si source gas spreading nozzle 27 for a time period T5. Thus, Sisource is adhered to the wafers W. Here, for example, the time period T5may be from 10 seconds to 60 seconds. Furthermore, for example, the fluxof Si source gas may be from about 50 mL/min(sccm) to about 300mL/min(sccm). Furthermore, the internal pressure of the processingvessel 1 may be from about 10 Pa to about 100 Pa.

The operation S7 of supplying an oxidizer is same as the operation S3.Furthermore, the operations S6 and S8 of purging the interior of theprocessing vessel 1 by supplying purge gas are same as the operation S2and S4. The operation S6 after the operation S5 of supplying Si sourcegas and the operation S8 after the operation S7 of supplying an oxidizermay employ respectively different time periods for vacuum-sucking andsupplying purge gas, in consideration of a difference between thedegrees of exhaustions of gases in the operations S5 and S7. Moreparticularly, time periods regarding the operation S6 may be longer thanthose regarding the operation S8, because it takes longer time period toexhaust gas after the operation S5.

Accordingly, a zirconia-based film doped with from about 1 atm % toabout 4 atm % of Si may be formed by performing one or more cycles, eachof which includes formation of a ZrO₂ film, which becomes a base, due toalternate supply of Zr source gas and an oxidizer for a plural number oftimes and formation of a SiO₂ film due to alternate supply of Si sourcegas and an oxidizer once or plural number of times, and by performingannealing operation thereafter if necessary. Thus, the zirconia-basedfilm may maintain zirconia crystals, and thus the zirconia-based filmmay maintain high permittivity and may reduce leakage currentsignificantly. It is presumed that, since Si of such small quantityexists in grain boundaries of zirconia crystal, the zirconia crystal maynot be damaged. Furthermore, it is presumed that, since the Si coversthe grain boundaries of the zirconia crystal, leakage from the grainboundaries of zirconia crystals may be prevented. Furthermore,containment of about 3 atm % of Si in a zirconia-based film increaseszirconia crystal grain and thus reduces grain boundaries. This alsocontributes to prevent the leakage from the grain boundaries of zirconiacrystals. Furthermore, increase in zirconia crystal grain contributes toincreases in permittivity. Thus, the zirconia-based film containingabout 3 atm % of Si exhibits higher permittivity than a zirconia filmcontaining no Si, and also exhibits an excellent characteristic thatleakage current of the zirconia-based film containing about 3 atm % ofSi is approximately 100 times less than that of the zirconia filmcontaining no Si.

Next, an experiment, which is the basis of the present invention, willbe described below.

In the experiment, a film was formed on a wafer by using the filmforming apparatus 100 of FIG. 1 according to the timing chart shown inFIG. 3, wherein TEMAZ was used as Zr source, 3DMAS was used as Sisource, and O₃ gas was used as an oxidizer.

A zirconia-based film was formed by adjusting Si concentration of thezirconia-based film due to changes of the number of times, x, the ZrO₂film forming sequence is repeated, and the number of times, y, the SiO₂film forming sequence is repeated and thus by adjusting the total numberof cycles, z, such that the zirconia-based film has a predeterminedoverall thickness. Then, the obtained film was annealed at 450° C. for30 minutes in the processing vessel 1 containing N₂ atmosphere of 1 Torr(133.3 Pa).

As a sample 1, a film was formed to have an overall thickness of 13.76nm by using x=11, y=1, and z=8. As a sample 2, a film was formed to havean overall thickness of 13.80 nm by using x=5, y=1, and z=16. As asample 3, a film was formed to have an overall thickness of 13.00 nm byusing x=3, y=1, and z=25. When Si concentrations of the samples 1through 3 were analyzed using the Rutherford backscattering spectroscopy(RBS), Si concentration of the sample 1 was 3.1 atm %, Si concentrationof the sample 2 was 5.5 atm %, and Si concentration of the sample 3 was8.5 atm %. The relationship between (y/(x+y)×100)(%) and Siconcentration of FIG. 4 is based on the result of the analysis.

Other than the samples 1 through 3, a film was formed as a sample 4 tohave Si concentration of 4 atm % and a thickness of 12.80 nm by usingx=9, y=1, and z=9, a film was formed as a sample 5 to have Siconcentration of 2 atm % and a thickness of 13.80 nm by using x=18, y=1,and z=5, and a film was formed as a sample 6 to have Si concentration of0 atm % and a thickness of 12.90 nm by repeating only the ZrO₂ filmforming sequence 86 times. Then, relative permittivity and leakagecurrent of each of the samples 4 through 6 were measured. Here, themeasured leakage current corresponds to leakage current when voltage of1 V is applied. Results of the measurements are arranged in FIG. 5. FIG.5 is a graph showing relationships among Si concentration of a film,permittivity of the film, and leak current of the film, wherein thehorizontal axis indicates Si concentration of a film, and the verticalaxes indicate relative permittivity and leakage current. As shown inFIG. 5, as the Si concentration rises from zero, the relativepermittivity tends to increase, whereas the leakage current tends todecrease. When the Si concentration is 3.1 atm %, the relativepermittivity is at the peak being about 25. When the Si concentrationexceeds 3.1 atm %, the relative permittivity decreases. When the Siconcentration is 4 atm %, the relative permittivity is almost same asthe sample 6 which contains no Si. When the Si concentration exceeds 4atm %, the relative permittivity becomes even lower than the sample 6which contains no Si. Meanwhile, the leakage current rapidly decreasesas the Si concentration approaches to 2 atm %, and decreases furtherwhen the Si concentration is 2 atm % or greater. While the leakagecurrent of the sample 6 which contains no Si was 1×10⁻⁷ A/cm², leakagecurrent of a film of which Si concentration is 2 atm % or greater was10⁻⁹ A/cm² order or less, and thus the leakage current of the film ofwhich Si concentration is 2 atm % or greater was approximately 100 timesless than that of the sample 6. Although there is no plot when Siconcentration is 1 atm %, FIG. 5 shows that 1 atm % of Si concentrationis sufficiently effective.

Next, structures of films were observed using a transmission electronmicroscope (TEM) with respect to the sample 6 (Si=0 atm %), a sample 1(Si=3.1 atm %), and a sample 2 (Si=5.5 atm %). Results of theobservation are shown in FIG. 6. FIG. 6 shows TEM photographs ofcross-sections and top views of the samples. It is confirmed thatcrystals are clearly observed in the sample 6 which contains no Si andin the sample 1 of which Si concentration is 3.1 atm %, whereas crystalsare not observed in the sample 2 of which Si concentration is 5.5 atm %,and the sample 2 is in amorphous state. Furthermore, it is confirmedthat the crystal of the sample 1 was larger than the crystals of thesample 6.

Next, crystal structures of the sample 6 (Si=0 atm %) and the sample 1(Si=3.1 atm %), in which crystals were observed, were confirmed by usingelectron beam diffraction. Here, ratio of crystals were calculated froma diffraction strength of the peak and a “d” value that are obtainedfrom the electron beam diffraction. Results of the calculation are shownin FIG. 7. As shown in FIG. 7, crystal structures of the films are cubicand tetragonal.

According to the results, it is confirmed that zirconia crystals are notsignificantly affected and maintains a crystal structure even if a smallquantity of Si is added, whereas zirconia crystals are not maintainedand become amorphous when Si concentration increases.

Next, different Si concentrations due to different Si sources will bedescribed. Here, a difference between a relationship between y/(x+y)×100and Si concentration in case where the 3DMAS is used as Si source and arelationship between y/(x+y)×100 and Si concentration in case where the4DMAS is used as Si source was checked. The difference is shown in FIG.8. As shown in FIG. 8, when films are formed under same conditions, itis confirmed that Si concentration of the case in which 4DMAS is used islower than that of the case in which 3DMAS is used.

According to the present invention, zirconia-based film may be formed byusing ALD technique in which silicon of 1˜4 atm % is added to zirconia.Thus, grain boundary leakage may be suppressed while maintainingzirconia crystal. Therefore, zirconia-based film which has bothcharacteristics of high permittivity and low leakage-current may beformed.

Furthermore, the present invention is not limited to the aboveembodiment, and various changes may be made therein. For example,although it is shown that the above embodiment is applied to a batchtype film-forming apparatus, which is loaded with a plurality of wafersand performs film formations on the wafers in bulk, the above embodimentis not limited thereto and may be applied to a single type film-formingapparatus, which performs forms a film on a single wafer at a time.

Furthermore, although organic metal compounds are used as Zr source andSi source in the above embodiment, the above embodiment is not limitedthereto, and inorganic metal compounds may also be used. However, it ismore efficient to use organic metal compounds, which generate a largequantity of gas, as metal sources.

Furthermore, an object to be processed is not limited to a semiconductorwafer, and the present invention may also be applied to other types ofsubstrates, such as an LCD glass substrate.

While this invention has been particularly shown and described withreference to exemplary embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention as defined by the appended claims.

1. A film forming method comprising: inserting objects to be processedinto a processing vessel that can be maintained vacuum, and making theprocessing vessel vacuum; performing a sequence of forming a ZrO₂ filmon a substrate by alternately supplying a zirconium source and anoxidizer to the processing vessel a plurality of times and performing asequence of forming a SiO₂ film on the substrate by alternatelysupplying a silicon source and the oxidizer to the processing vessel oneor more times, wherein the number of times of performances of each ofthe sequences is adjusted such that Si concentration of the films isfrom about 1 atm % to about 4 atm %; and forming a zirconia-based filmhaving a predetermined thickness by performing the film formingsequences for one or more cycles, wherein one cycle indicates that eachof the ZrO₂ film forming sequences and the SiO₂ film forming sequencesare repeated the adjusted number of times of performances.
 2. The filmforming method of claim 1, wherein the number of times the zirconiumsource and the oxidizer are supplied during the formation of the ZrO₂film and the number of times the silicon source and the oxidizer aresupplied during the formation of the SiO₂ film are adjusted such thatthe Si concentration of each of the films is from about 2 atm % to about4 atm %.
 3. The film forming method of claim 1, wherein a gas remainingin the processing vessel is exhausted between the supplying of thezirconium source and the supplying of the oxidizer and between thesupplying of the silicon source and the supplying of the oxidizer. 4.The film forming method of claim 1, wherein, after forming thezirconia-based film, the obtained films are annealed at a temperaturelower than or equal to 450° C.
 5. The film forming method of claim 1,wherein the oxidizer is at least one selected from the group consistingof O₃ gas, H₂O gas, O₂ gas, NO₂ gas, NO gas, N₂O gas, and a radical ofO₂ gas and H₂ gas.
 6. The film forming method of claim 1, wherein thezirconium source and the silicon source are organic metal compounds. 7.The film forming method of claim 1, wherein a formed zirconia-based filmhas zirconia crystals.
 8. The film forming method of claim 1, whereinthe Si concentration of the films is adjusted in proportion to a ratioof the number of times which the Si source is supplied.
 9. A filmforming apparatus for forming a metal oxide layer with respect toobjects to be processed, the film forming apparatus comprising: avertically cylindrical processing vessel which can be maintained vacuum;a supporting unit which supports the objects to be processed within theprocessing vessel; a heating unit which is formed to surround the outersurface of the processing vessel; a zirconium source supplying unitwhich supplies a zirconium source to the processing vessel; a siliconsource supplying unit which supplies a silicon source to the processingvessel; an oxidizer supplying unit which supplies an oxidizer to theprocessing vessel; and a control unit which controls the zirconiumsource supplying unit, the silicon source supplying unit, and theoxidizer supplying unit, wherein the control unit controls the filmforming apparatus: to insert the objects to be processed into aprocessing vessel, which can be maintained vacuum, to make theprocessing vessel vacuum; to perform a sequence of forming a ZrO₂ filmon a substrate by alternately supplying the zirconium source and anoxidizer to the processing vessel a plurality of times and to perform asequence of forming a SiO₂ film on the substrate by alternatelysupplying the silicon source and the oxidizer to the processing vesselone or more times, wherein the number of times of performances of eachof the sequences is adjusted such that Si concentration of the films isfrom about 1 atm % to about 4 atm %; and to perform the film formingsequences for one or more cycles, wherein one cycle indicates that eachof the ZrO₂ film forming sequences and the SiO₂ film forming sequencesare repeated the adjusted number of times of performances.
 10. The filmforming apparatus of claim 9, wherein the control unit controls the filmforming apparatus such that the number of times the zirconium source andthe oxidizer are supplied during the formation of the ZrO₂ film and thenumber of times the silicon source and the oxidizer are supplied duringthe formation of the SiO₂ film are adjusted, so that the Siconcentration of each of the films is from about 2 atm % to about 4 atm%.
 11. The film forming apparatus of claim 9, wherein the control unitcontrols the film forming apparatus such that a gas remaining in theprocessing vessel is exhausted between the supplying of the zirconiumsource and the supplying of the oxidizer and between the supplying ofthe silicon source and the supplying of the oxidizer.
 12. The filmforming apparatus of claim 9, wherein, after forming zirconia-based filmcomprising the ZrO₂ film and the SiO₂ film, the control unit controlsthe film forming apparatus such that the obtained films are annealed ata temperature lower than or equal to 450° C.
 13. The film formingapparatus of claim 9, wherein the Si concentration of the films isadjusted in proportion to a ratio of the number of times which the Sisource is supplied.
 14. A computer readable recording medium havingrecorded thereon a computer program for executing the film formingmethod of claim 1.